The resection of large area turnouts in the gastrointestinal tract which are restricted to the mucosa should be carried out in one session and the tumours must be as fully excised as possible. Conventionally, the snare technique or the cap technique is used to achieve these goals, however, with these techniques, varying sizes of circular operative specimens can only be produced by varying the snare diameter or the cap diameter. Therefore, large area turnouts with a diameter of more than 8 cm can only be removed using a piecemeal technique. However, complete excision of large area turnouts is desired. To this end, some first methods have been used wherein the mucosa has been cut into a round, piece-by-piece, with a flexible needle and then completely removed. In this process, the resection must take place in the submucosa. The layer thicknesses are approximately 0.5 mm to 1.5 mm.
During endoscopic mucosa resection, bleeding and perforation of the intestinal or gastric wall can occur. In order to tackle these problems, liquid is injected under the mucosa with a flexible needle before the resection. The needle must be precisely placed within the submucosa. The penetration of the liquid into the mucosa causes the mucosa to be loosened from the Muscularis propria and forms a liquid cushion forms beneath the mucosa. This produces a safety separation from the Muscularis propria as well as a heat barrier. The mucosa resection is then carried out with a flexible needle knife. A suitable device for endoscopic injection of a liquid underneath the mucosa is described, for example, in DE 19 607 922 C2.
This technique for resection is extremely difficult and the operation duration for interventions of this type is currently between 2 and 6 hours. In particular, the difficulty of this type of intervention is that the injected liquid slowly leaks out of the submucosa during the operation, causing the Muscularis propria to become thermally damaged by the needle. This thermal damage can in turn lead to perforation of the intestine. In order to avoid this perforation, the instrument must be removed several times during the resection procedure and liquid must again be injected under the mucosa.
Alternative solutions to the problems of bleeding and intestinal perforation are being tested wherein liquids of different viscosity are used which leak out of the mucosa more slowly. However, these attempts still do not offer a satisfactory solution because the escape of the liquid out of the submucosa is only slowed, but not prevented.
It is therefore an object of the invention to provide a surgical instrument which may to facilitate endoscopic interventions, such as mucosa resection, wherein damage to the surrounding tissues, particularly the intestinal or gastric wall, may be reliably avoided.